1. Field of the Invention
The present invention relates to an information processing system, a server device and an information processing device which transmits a request to a server designated by a client in an environment where the workload is distributed to a plurality of servers.
2. Description of the Related Art
Computers are becoming more widespread along with performance improvement and cost reduction, and they now have important roles in the current business operations of corporations and the like. The use of computers has changed in the following way.
In the early days, the most commonly seen scheme was a centralized model where a large-sized computer was used from terminal apparatuses.
After some time, sophisticated small-sized machines arrived, significantly improving the performance of what individual users could afford. Thanks to this development, the conventional model of centralized server handling all the work was replaced by a decentralized client/server model where each personal computer terminal carries out some of the work previously handled by the central server. In the client/server model, however, if a large number of users existed, it was hard to maintain and manage applications running on the large number of client machines.
During the period when the client/server model was mainstream, the internet technology came along. The Internet made a dramatic progress, and a field of Web applications was established. The Web application indicates a Web-based application technology using the Web technology and LAN/WAN technology based on TCP/IP. This technology was used only for providing static content at first. That is, a Web server at an early stage almost simply transmitted stored contents (documents). Then, a technique of running software such as CGI or Servlet on a Web server was developed so that a user can receive an instruction from a client, interpret it, and dynamically display data to the client. This allows running of an application on the Web system, and the Web technology has changed from a one-sided information providing means to a means such as a client/server system that is usable as a platform of an application. That is, a Web server can use a mechanism to activate a program in response to a request from the Web browser of a client by using CGI or Servlet. The Web server can dynamically generate contents on the basis of a program processing result by data input from the client and send the contents. Any Web application (Web service) can run on the Web. That is, the client side can use a desired application only by preparing a Web browser without installing any specific commercial application. Examples of typical software/services are an electronic store that provides an enormous amount of merchandise information and a document keeping service.
The Web application is more advantageous than the conventional client/server model because the client side uses only a Web browser common to operations and can therefore reduce the application maintenance/management cost. For this reason, a Web system is becoming an important service platform. At the beginning, a service of a Web system generally uses a single server configuration. However, malfunction of the single server stops the whole service, seriously affecting the business activity.
To prevent this, a service that requires year-round offer generally employs a redundant configuration to make a plurality of servers to offer the service. To attain higher system performance, it is also necessary to distribute workload to a plurality of servers.
However, even in a system built using a plurality of servers, a problem may be posed if a series of operations is carried out within one server (to be referred to as a “single session” hereinafter). To prevent this, a system has been implemented in which individual server information is embedded in cookie information, and a single server processes a single session by using a load distribution apparatus on the basis of the information (Japanese Patent Laid-Open No. 2003-256310). FIG. 1 is a block diagram showing the configuration of a conventional Web service system that causes a single server to process a single session by using a load distribution apparatus.
Even in the distributed environment built using a plurality of servers, to conduct, e.g., an operation check test, it is necessary to connect a specific server designated from a client. The method of connecting to a specific server includes, e.g., the following two solutions.
As the first solution, an IP address dedicated to access is given to each server, and operation check is executed by connecting to each address. In this method, however, the description of the IP addresses individually assigned to the hosts file of the client must be changed upon the operation test, resulting in poor operation efficiency. The host file describes the correlation between a host name and an IP address. Name resolution on a network is done by referring to this file.
As the second solution, cookie information is forcibly changed on a client's browser after access. This method rewrites communication data (packet) by using a dedicated network tool. This method however requires many procedures for change. The operation efficiency becomes low in confirming connection to a number of servers. The cookie indicates a mechanism to exchange information such as user information and access log between a Web browser and a Web server. There is a cookie which has a text format and is saved in a cache area for a client's Web browser. There is also a temporary cookie that is used only upon communication between two web servers and is not saved in a cache area. The Web technology generally uses cookie. A cookie is generally created on the Web client side and saved. The data saved at this time contains the name, value, and term of validity of the cookie and an effective domain/path. When a cookie is created, the browser on the client side checks whether a designated URL matches the effective domain/path of the cookie. If they match, the browser implicitly transmits the cookie data to the server side. When a cookie is used, and the client implicitly transmits the cookie information to the Web server side upon the next access or session, the Web server can identify that it is an access from a specific client.